1. Field of the Invention
The present invention relates, in general, to a seat belt tensioner that increases the restraining force of a seat belt in order to protect a passenger in the event that a vehicle is involved in a collision.
2. Description of Related Art
In the event that a vehicle is involved in a collision, a passenger is often thrown forward with a considerable force, even when wearing a seat belt. A seat belt tensioner is a mechanism that increases the restraining force of a seat belt to protect the passenger before this forward throwing phenomenon occurs.
A seat belt tensioner will generally be described with reference to the seat belt mechanism shown in FIG. 1.
Typically, the seat belt mechanism is designed so that, when a buckle tongue 3 of the seat belt is fastened to a buckle 4 fixed on the side of a seat 1, an upper belt B1 restrains a passenger from the shoulder to the waist across the chest, and a lower belt B2 restrains the waist of the passenger. A belt tensioner 5 is connected to the upper belt B1, and is mounted in a center pillar trim 2. The lower belt B2 is fixedly installed below the belt tensioner 5 in the center pillar trim 2.
In this manner, when the belt tensioner 5 is installed on the upper belt B1 only, the upper belt B1 is first tensioned by the belt tensioner 5 in the event of the collision, and then the lower belt B2 performs restraint. Thus, according to the circumstances, the lower belt B2 is loose in spite of the operation of the belt tensioner 5, so that the hips and knees of the passenger move forward. In order to solve this problem, it is necessary to install the belt tensioner 5 on either the buckle 4 or the fixed end of the lower belt B2. The present invention particularly relates to a belt tensioner 5 that is to be mounted at this position.
Meanwhile, in conjunction with the present invention, Japanese Patent Application Publication No. 1996-164821 (published on Jun. 28, 1996), and U.S. Patent Application Publication No. 2003-0090101 (published on May 15, 2003) can be referred to as cross references.
The information disclosed in this Background of the Invention section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.